<!DOCTYPE html>
<html>
  <head>
    <style>
      #container {
        background: blue;
        height: 180px;
        width: 240px;
      }

      #box {
        background: green;
        height: 90px;
        width: 120px;
      }
    </style>
  </head>
  <body>
    <div id="container">
      <div id="box">
      </div>
    </div>
  </body>
</html>
